The study of rockets is an excellent way for students
to learn the basics of
forces
and the
response
of an object to external forces.
In flight, a rocket is subjected to the
forces of weight,thrust, and aerodynamics.
On this slide,
we have removed the outer "skin"
so that we can see the parts that make a rocket.
There are many parts that make up a rocket. For design and
analysis, engineers group parts which have the same function
into systems.
There are four major systems in a full scale rocket; the
structural system, the
payload system, the
guidance system, and the
propulsion system.

The structural system, or frame, is similar to the
fuselage of an airplane.
The frame is made from very strong but light weight materials, like
titanium or aluminum, and usually employs long "stringers" which run from
the top to the bottom which are connected to "hoops" which run around around
the circumference. The "skin" is then attached to the stringers and hoops to
form the basic shape of the rocket. The skin may be coated with a thermal
protection system to keep out the heat of air friction during flight and to
keep in the cold temperatures needed for certain fuels and oxidizers.
Fins are attached to some rockets at the bottom of the frame to provide
stability
during the flight.

The payload system of a rocket depends on the rocket's mission.
The earliest payloads on rockets were fireworks for celebrating
holidays.
The payload of the German V2, shown in the figure,
was several thousand pounds of explosives.
Following World War II, many countries developed guided
ballistic missiles
armed with nuclear warheads for payloads.
The same rockets were modified to launch satellites with a wide
range of missions; communications, weather monitoring, spying,
planetary exploration, and observatories, like the Hubble Space
Telescope. Special rockets were developed to launch people into
earth orbit
and onto the surface of the Moon.

The guidance system of a rocket may include very sophisticated
sensors, on-board computers, radars, and communication equipment
to maneuver the rocket in flight.
Many different
methods
have been developed to control rockets in flight.
The V2 guidance system included small vanes in the exhaust of the
nozzle to deflect
the thrust from the engine.
Modern rockets typically
rotate
the nozzle to maneuver the rocket.
The guidance system must also provide some level of
stability so that the rocket does
not tumble in flight.

As you can see on the figure, most of a full scale
rocket is propulsion system.
There are two main classes of propulsion systems,
liquid rocket engines and
solid rocket engines.
The V2 used a liquid rocket engine consisting of fuel and oxidizer (propellant)
tanks,
pumps, a combustion chamber with nozzle, and the associated plumbing. The
Space Shuttle, Delta II, and Titan III all use solid rocket strap-ons.

The various rocket parts described above have been grouped by function
into structure, payload, guidance, and propulsion systems. There are
other possible groupings. For the purpose of
weight determination
and flight
performance, engineers often group the payload,
structure, propulsion structure (nozzle, pumps, tanks, etc.),
and guidance into a
single empty weight paramter. The remaining propellant weight
then becomes the only factor that changes with time when determining
rocket performance.